A series of 5' promoter deletions of the RAS2 gene has been analyzed to investigate its complex transcriptional regulation in the yeast Saccharomyces cerevisiae. Two positive transcriptional regulatory elements were identified: element A and element B. Element A regulates two of the three RAS2 promoters. This element is capable of activating a heterologous promoter and contains two copies of the sequence CCTCGCCCC. Each of the 9 bp C rich repeats of element A is part of a sequence with extensive homology to a transcriptional regulatory element upstream of the human epidermal growth factor receptor (EGFR) gene. Element B contains a tandem duplication of a 21 nucleotide sequence and activates the third RAS2 promoter in the absence of Element A.